PESHAWAR, Pakistan, Jan. 9 -- Even as his reputation has grown more menacing and his militia more powerful, the Taliban commander accused of ordering the death of Benazir Bhutto has shrouded himself in mystery.

When Baitullah Mehsud attended a February 2005 signing ceremony for an ill-fated cease-fire with the Pakistani government, he bundled his face and upper body in a black cloth before appearing in public to scrawl his signature. Like the man to whom he has sworn allegiance, Afghan Taliban leader Mohammad Omar, Mehsud has obsessively avoided cameras and maintained an ascetic lifestyle.

Since then, Mehsud has emerged as perhaps the greatest military threat to the Pakistani government. Last August, just weeks after the cease-fire ended in recriminations, his fighters from South Waziristan stunned the country by capturing a group of more than 200 soldiers who were patrolling the lawless tribal areas along the border with Afghanistan. Three were executed; the rest were freed in a prisoner swap.

In recent days, Pakistani officials have blamed the Taliban commander for the death of Bhutto, the former prime minister who was killed Dec. 27 while campaigning to return to power. Investigations are ongoing, and it remains to be seen whether Mehsud was directly responsible.

What is clear, however, is that Pakistan's past efforts to control or neutralize Mehsud have repeatedly backfired, leaving him stronger than ever and adding to the general instability that is plaguing the country, Pakistani officials and analysts said in interviews.

"Baitullah Mehsud is the biggest problem of today's Pakistan, and he is the main factor behind the failure of the government's current policies in the tribal region," a senior government official said on condition of anonymity in Peshawar, a frontier city near the Afghan border. "Kidnap after kidnap of the security forces by his militants has become a routine matter now and a big embarrassment for the government."

Mehsud, 34, is also accused by Afghan and U.S. officials of organizing suicide attacks in Afghanistan and helping to supply Taliban fighters there. But the Pakistani military, distracted by political problems, has been reluctant to mount a direct assault on his refuge in South Waziristan, a rugged tribal area that has successfully resisted outside control for centuries.

"There's really no choice for the government now," said Muhammed Amir Rana, director of the Pak Institute for Peace Studies in Islamabad. "They'll have to go in and do a military operation to weaken him. He's become too strong. They need to do something to stop the Taliban and the Talibanization of that region."

Analysts and officials said there are other Taliban commanders who control more territory or bigger forces than Mehsud. But they said his political influence within the notoriously fractious movement has grown rapidly and is probably unparalleled on the Pakistani side of the border.

Last month, for instance, Mehsud was chosen to serve as the head of a 40-member shura, or consultative council, that was formed to coordinate various Taliban factions in Pakistan.

Mehsud is also a favorite commander of Taliban leaders in Afghanistan, including Omar, the one-eyed cleric who has led the movement for a decade, and Jalaluddin Haqqani, a grizzled insurgent leader who has organized attacks against Soviet, U.S. and NATO troops there since the 1980s.

"There are a couple of other local Taliban commanders who have been influential in their own localities, but Baitullah has overshadowed them all lately and now his name carries the day when it comes to militancy in Pakistan," said Ashraf Ali, a researcher at Peshawar University and specialist on the Taliban.